Variable resistance device



Jan. 9, 1951 w. R. JACK Er AL 2,537,671

VARIABLE RESISTANCE DEVICE Filed March 10, 1950 INVENTORJ I 5 gyivsur 0,0001;

ATTORNEY Pltentcd Jan. 9, 1951 7 UNITED sT-Arss vanianui RESISTANCE DEVICE William a. Jack and Lnle 1). com, Chagrin Falls, and Emil M. .Brinker, Lakewood, 01110; said Cahill and said Brinke'r alsignors to said Jack Application 10,1950, seiamb. 148,894

V (Cl. 201555 V 19 Claims. 1 This invention relates to resistance devices and.

' movably the casingby screw bolts 3.

has for one of its primary objectsto provide a variable resistance devicecapable of permanent operation and having a wide range 'ofresistance. In the conventional resistance'elements various materials are employed as single or multiple coatings on a ceramic base. Due to the selection of resistance materials and the methods employed in applying them to the base, inherent weaknesses in the resistance materials develop due to heat, oxidation and other atmospheric eifects and excessive wear by the contactor, leaving it difllcult, if not impossible to obtain uniformity of the variable resistance device or its accurate control.

It is therefore an object of this invention to provide a variable resistance device in which the pended claims, certain embodiments-thereof be-' ing illustrated in the accompanying drawings, in which:

Figure 1 is an end view of the variable resistance device, with the cover plate shown partly broken away; Y

Figure 2 is a view in longitudinal section of the same;

Figure 3 is a view in perspectiveot-the. ring,

Suitably positioned within the casing I is a cylindrical'potentiometer ring comprising a base l and'a' resistance material structure, generally indicated 'at,5, on the inside surface of the base. The casing-also has an externally screw threaded sleeve 6 for the proper mounting of the unit -wherever desired and shaft I is mounted to be rotatable therein. shaft 1 carries a flange 8 that carries a resilient arm 9 provided with a ball I0 urged against contact element II ofterminal I2. Terminal I3 has a resilient member I4 in contact with r the potentiometer ring. Flange 8 also carries a contactor, generally indicated at I5, urged into constant contact with the inner surface of "the resistance material structure on the inside of the potentiometer ring.

while the base 4 maybe ceramic, glass, or other material, for purposes of illustration it will be referred-to as a glass cylinder; As previously 'stated we desire to obtain a potentiometer ring having a resistance material structure that is virtually an integral part thereof. This we propose to accomplish, for instance, by evaporating a resistance metal on to the inner surface 'of the glass ring, For purposes of illustration, platinum will be discussed as preferable. In order to evaporate the platinum on .to and into the glass we heat theplatinum to a temperature above its boilingpoint in a. vacuum and apply a potential between the evaporating metal and the glass bowl. An'alternatemethodis known as sputtering in which the cathode material is not heated,

but a high potential between the anode and the cathode isused. Such evaporated metal procvesses are readily controllable to insure imbedpartly broken away, showing a potentiometer formcd of a'base with a resistance material 'struc ture of uniform thickness and varying width;

Figure 4 is a similar view in which the resistance material structure is of varying thickness and uniform width;

Figure 5 is a schematic view showing a. resistance device in which there are multiple layers of resistance material applied to the base and a contactor having a ball and socket suspended contacting member; and

Figure 6 is a similar view of a base with one layer of resistance material and a contactor with and the single platinum layer is a contacting member formed of a globule of mercury.

Referring more particularly to the drawings,

ding of the platinum into the glass bowl and provide a coating whose thickness and width is also' 'readily controllable for any desired pattern of varyingthickness or width or both. A single layer resistance material structure is .shown in Figure 6, in which the glass bowl is shown at 4 shown exaggerated in thickness at Iii. r

As an example of a multiple layer resistance material structure, we have shown in Figure 5 in which the glass bowl is shown also at 4. ,To the glass bowl we apply a thin coating by evaporating thereon nickel nor-aluminum, I! as an ex cellent adhesive binder. On .the. binder I! we evaporate a thick layer I8 ofre'sistance metal such as Nichrome alloy and to layer I8 weevapcrate a very thin layer I 9 of platinum.

The contactor, generally referred to at I in Figures 1 and 2, may take various form. two of which are illustrated in Figures and 6. In Figure 5 there is shown a portion of a carrying arm 2!, inside of which is a screw plug 28, a spring I! and a ball and socket suspended platinum ball contactor 20. In Figure 6 is the same arm 11, screw plug I8 and spring is with a piston II and globule of mercury 22.

In Figure 3 the resistance material structure, generally referred to at Ii, is intended to represent such a structure, whether of a single or multiple layers, that varies in width from its narrow end 23 to its adjacent relatively wider end 24.

In Figure 4 the resistance material structure, generally indicated at 5, is intended to represent such a structure, whether of a single or multiple layers, that varies in thickness from its thin end I! to its adjacent relatively thicker end 26. It is to be understood that any pattern of varying thickness and width, or both, may be employed.

In connection with the single layer resistance material structure shown in Figure 4, platinum was selected as an excellent choice inasmuch as it may be evaporated into and onto the glass bowl to form a coating that will not oxidize and form a good contact surface for either the platinum rolling ball or the mercury globule 22 without wear or chemical attack.

In connection with the multiple layer resistance material structure shown in Figure 3, the thin aluminum layer I1 is an excellent adhesive binder H on the glass bowl I and the thick Nichrome alloy layer I8 is an excellent resistance metal for use in variable resistance devices. However,

Nichrome alloy is readily bonded by evaporation to aluminum but not as much so to glass as is aluminum. Moreover, as good a resistance metal as Nichrome alloy is, it is subject to oxidation and other atmospheric effects and also subject to chemical attack by mercury, if a contactor, such as shown in Figure 6, were used. Hence, we evaporate a very thin layer iii of platinum on the Nichrome alloy layer l8 and the platinum and aluminum layer l9 may be so thin as to not appreciably interfere with the good resistance characteristics of the Nichrome alloy layer. The thin platinum layer l9 also affords an excellent contact surface for the frictionless engagement of either the ball and socket platinum ball 20 or the mercury globule 22.

Thus, whether the resistance metal is the single layer of Figure 6, the multiple layer of Figure 5, the varying width type of Figure 3, the varying thickness type of Figure 4 or one in which the pattern of the resistance structure varies both in thickness and width, the top layer being of platinum, it is suitable for engagement by either ball 20 or globule 22, as neither of the latter are abrasive nor do they produce chemoelectrical or thermoelectrical forces or oxidation.

It will be seen from the foregoing that we have provided an efllcient continuously variable resistance device of permanent non-wearing and nondeteriorating characteristics capable of carrying high currents for use for any mathematical function, whether linear or non-linear.

We claim: I

1. A variable resistance device including a base provided with a resistance structure consisting solely of resistance metal evaporated on said base and a movable contacting member to engage said evaporated resistance metal.

2. A variable resistance device including an inill said base and a movable contacting member to engage said evaporated resistance metal.

3. A variable resistance device including an insulating base provided with a resistance structure consisting solely of resistance metal impervious to oxidation evaporated on said base and a movable contacting member to engage said evaporated resistance metal.

4. A variable resistance device including an insulating base provided with a resistance structure consisting solely of resistance metal impervious to oxidation evaporated on said base and a movable contacting member to engage said evaporated resistance metal, said evaporated resistance metal varying in thickness throughout its length.

5. A variable resistance device including an insulating base provided with a resistance structure consisting solely of resistance metal impervious to oxidation evaporated on said base and a movable contacting member to engage said evaporated resistance metal, said evaporated resistance metal varying in width throughout its length.

6. A variable resistance device including an insulating base provided with a resistance structure consisting solely of resistance metal impervious to oxidation evaporated on said base and a movable contacting member to engage said evaporated resistance metal, said evaporated resistance metal varying in thickness and width throughout its length.

7. A variable resistance device including a base of glass provided with a coating of platinum as a resistance metal evaporated on said base and a movable contacting member to engage said platinum coating only.

8. A variable resistance device including a base of glass provided with a coating of platinum as a resistance metal evaporated on said base and a movable contacting member to engage said platinum coating only, said contacting member being of platinum.

9. A variable resistance device including a.

her being of mercury.

10. A variable resistance device including an insulating base provided with a resistance structure consisting solely of resistance metal impervious to oxidation evaporated on said base and a: movable contacting member to engage said evaporated resistance metal, said evaporated resistance metal and said contacting member being impervious to chemical reaction by each other by reason of contact.

11. A variable resistance device including an insulating base provided with a resistance metal structure consisting solely of an initial thin coating of metal having high adhesive qualities for said base, said initial coating being evaporated on said base, a second thick coating of metal of desired resistance characteristics evaporated on said initial coating, 9. third thin layer of resistance metal impervious to oxidation evaporated on said second coating and a movable contacting device to engage said third coating.

12'. A variable resistance device including an insulating base provided with a resistance metal structure comprising an initial thin coating of metal having high adhesive qualities for said base, said initial coating being evaporated on said base, a second thick coating of metal 01' desired resistance characteristics evaporated on saidinitial coating, a third thin layer of resistsired resistance characteristics evaporated on said initial coating, a third thin layer of resistance metal impervious to oxidation evaporated on said second coating and a movable contacting device to engage said third coating, said resistance metal structure varying in thickness throughout its length.

14. A variable resistance device including an insulating base provided with a resistance metal structure comprising an initial thin coating of metal having high adhesive qualities for said base, said initial coating being evaporated on said base, a second thick coating of metal of desired resistance characteristics evaporated on said initial coating, a third thin layer 01' resistance metal impervious to oxidation evaporated on said second coating and a movable contacting device to engage said third coating, said "resistance metal structure varying in thickness and width throughout its length.

15. A variable resistance device including a. glass base provided with a resistance metal structure comprising an initial thin coating of aluminum evaporated on said base, a second thick coating of Nichrome alloy evaporated on said aluminum coating, a third thin coating of platinum evaporated on said Nichrome alloy coating and a movable contacting member of platinum to engage said platinum coating.

16. A variable resistance device including a glass base provided with a resistance metal structure comprising an initial thin coating of aluminum evaporated on said base, a second thick coating of Nichrome alloy evaporated on said aluminum coating, a third thin coating of platinum evaporated on said Nichrome alloy coating and a movable contacting member comprising a globule of mercury for contacting said platinum coating.

17. A variable resistance device including a glass base provided with a resistance metal struciii ture comprising an initial thin coating of aluminum evaporated on said base, a second thick coating of Nichrome alloy evaporated on said aluminum coating, a third thin coating of platinum evaporated on said Nichrome alloy coating and a movable contacting member or platinum to engage said platinum coating, said resistance metal structure varying in thickness and width throughout its length.

18. A variable resistance device including a glass base provided with a resistance metal structure comprising an initial thin coating of aluminum evaporated on said base, a second thick coating of Nichrome alloy evaporated on said aluminum coating, a third thin coating of platinum evaporated on said Nichrome alloy coating and a movable contacting member comprising a globule of mercury for contacting said platinum coating, said resistance metal structure varying in thickness and width throughout its length.

19. A variable resistance device including a glass base provided with a resistance metal structure comprising an initial thin coating of aluminum evaporated on said base, a second thick coating of Nichrome alloy evaporated on said aluminum coating, a third thin coating of platinum evaporated on said Nichrome alloy coating, said resistance metal structure varying in width and thickness throughout its length and a movable contacting member of a metal chemically non-reactive with platinum for engaging sai platinum coating.

WILLIAM R. JACK. LYSLE D. CAHlLL. EMIL M. BRINKER.

REFERENCES CITED The following references are of record in the file of this patent: 

